基于MBS的剪式座椅垂向刚度特性比较分析

采用多体系统(MBS)动力学分析软件ProMECHANICA/Motion建立了剪式座椅悬架的仿真模型。基于此模型,比较了6种典型弹簧布置方式下的座椅垂向刚度特性,分析了2种典型弹簧布置方式下连接点位置变化对座椅垂向刚度特性的影响。仿真结果表明,多数弹簧布置方式下的剪式座椅垂向刚度具有明显的非线性特性,且其非线性特性在工作行程内表现为软特性,软特性的强弱程度随弹簧布置方式的不同而不同,弹簧倾斜布置于两剪杆之间或剪杆与座椅底板之间时,座椅垂向刚度软特性的强弱随弹簧连接点位置的变化而变化。     

10MW高温气冷堆乏燃料元件转运罐罐盖封压机构的研制

文章主要介绍10MW高温气冷堆（HTR-10）乏燃料元件转运罐罐盖封压机构的结构、功能、设计参数和工作原理。实验室和现场安装后的调试试验以及实际运行操作表明，该机构运行良好、可靠，完全满足HTR-10的使用和安全要求。     

10 kV配电线路带电作业导线遮蔽罩温升特性分析

导线遮蔽罩作为绝缘遮蔽用具已广泛运用于10 kV配电线路带电作业中,但遮蔽罩过热会影响其绝缘性能,威胁工作人员安全.利用有限体积法建立了导线遮蔽罩温度-流体场计算模型,研究了导线载流量、风速和日照强度等对软、硬质导线遮蔽罩温升的影响.结果 表明,额定负荷条件下,软、硬质遮蔽罩的最大温升分别为19.1、17.5K,硬质遮...     

冰盖条件下桥墩局部冲刷研究进展

冬季,寒冷地区的河流会出现冰盖或冰塞现象。冰盖的存在使水流湿周增加,流速剖面与明流条件下完全不同,最大流速出现在河床表面和冰盖底部之间,具体位置取决于河床和冰盖的相对粗糙程度。因此,冰盖条件下桥墩局部冲刷过程不同于明流条件下的局部冲刷过程。明流条件下的桥墩局部冲刷是国内外学者研究的热点问题之一,但关于冰盖条件下桥墩局部冲刷的研究工作却非常有限。在简要回顾明流条件下桥墩局部冲刷研究成果的基础上,对冰盖条件下桥墩局部冲刷的研究成果进行了综述和讨论,并提出了今后的研究方向。     

Study of human–seat interface pressure distribution under vertical vibration

The influence of whole-body vertical vibration on the dynamic human–seat interface pressure is investigated using a flexible grid of pressure sensors. The ischium pressure and the overall pressure distribution at the human–seat interface are evaluated as functions of the magnitude and frequency of vibration excitation, and seated posture and height. The dynamic pressure at the seat surface is measured under sinusoidal vertical vibration of different magnitudes in the 1–10 Hz frequency range. Two methods based on ischium pressure and ischium force are proposed to study the influence of seat height, posture and characteristics of vibration. The results of the study reveal that the amplitude of dynamic pressure component increases with an increase in the excitation amplitude in almost entire frequency range considered in this study. The dynamic components of both the ischium pressure and the ischium force reveal peaks in the 4 to 5 Hz frequency band, the range of primary resonant frequency of the seated human body in the vertical mode. The mean values of the dynamic ischium pressure and the ischium force remain constant, irrespective of the excitation frequency and amplitude. The magnitudes of mean pressure and force at the human–seat interface, however, are dependent upon the seat height and the subject's posture. The inter-subject variability of the static ischium pressure and effective contact area are presented as functions of the subject weight and subject weight-to-height ratio. It was found that heavy subjects tend to induce low ischium pressure as a result of increased effective contact area.

Relevance to industry

Pressure distribution at the human–seat interface has been found to be an important factor affecting the seating comfort and work efficiency of various workers. The study of human–seat interface pressure distribution under vibration is specifically critical to the comfort, work efficiency and health of vehicle drivers, who are regularly exposed to vibration. The results reported in this paper will be useful to study dynamic response of the interface pressure and design vehicle seats.     

基于覆盖粗糙集模型的层次聚类算法

目前大部分聚类算法只适用于处理属性取值为单值的数值型数据,介绍了一种新的基于粗糙集理论的聚类算法,该算法不仅可用于取值为单值的数值型数据聚类,而且能够用于取值为多值的非数值型数据聚类.该算法利用基于相容关系的属性最小覆盖来求解对象各属性的对象属性信息粒.在此基础上,通过对象属性信息粒和对象粗糙相似度的运算构建各对象的相容粒.最后,把具有相同相容粒的对象视为同一等价类,从而实现对论域的聚类,进而对数据对象进行层次聚类.实验结果表明,该算法是可行的.     

对象依赖集合性质的研究

在复杂对象模式的规范化设计中,对象间的语义关系起了重要作用。然而,目前还没有关系的研究报告,讨论了对象依赖集合的一些性质,首先概括了基本概念和性质;然后给出并证明获取一个OD集合所有关键字的JINGSI算法;最后证明要作为复杂对象模式规范化设计的MIMI算法输入的OD集合的特性,并基于此改进复杂对象模式规范化设计。     

一种优化逻辑函数的程序设计与实现

论文提出了EDA中易于计算机实现的逻辑函数优化方法,即在优化过程中引入删劣运算,用锐积运算求质蕴涵项,用选择提炼极值法求最小覆盖,并对循环函数进行处理的优化方法。设计了相应的组合逻辑电路逻辑综合优化程序,大量的测试证明了该方法的正确性和易于计算机实现的有效性。     

面向数控粗加工的自适应细分

为获得加工余量均匀的数控粗加工模型,提出了一种基于面误差的自适应细分算法.该算法以细分后的控制网格与极限曲面之间的最小距离和粗加工余量作比较,确定均匀细分次数.将均匀细分后的网格向极限曲面投影形成覆盖网格,再以覆盖网格和极限曲面之间的距离作为自适应细分准则,对不能满足精度的区域进行自适应细分.实验结果表明,在给定的精度范围内,该算法能够大幅度抑制细分过程中网格数量的快速增长,并能获得与原始算法光顺程度基本一致的曲面,大大提高了模型的后处理速度.     

Assessment of the MODIS LAI product for Australian ecosystems

The leaf area index (LAI) product from the Moderate Resolution Imaging Spectroradiometer (MODIS) is important for monitoring and modelling global change and terrestrial dynamics at many scales. The algorithm relies on spectral reflectances and a six biome land cover classification. Evaluation of the specific behaviour and performance of the product for regions of the globe such as Australia are needed to assist with product refinement and validation. We made an assessment of Collection 4 of the MODIS LAI product using four approaches: (a) assessment against a continental scale Structural Classification of Australian Vegetation (SCAV); (b) assessment against a continental scale land use classification (LUC); (c) assessment against historical field-based measurement of LAI collected prior to the Terra Mission; and (d) direct comparison of MODIS LAI with coincident field measurements of LAI, mostly from hemispherical photography. The MODIS LAI product produced a wide variety of geographically and structurally specific temporal response profiles between different classes and even for sub-groups within classes of the SCAV. Historical and concurrent field measurements indicated that MODIS LAI was giving reasonable estimates for LAI for most cover types and land use types, but that major overestimation of LAI occurs in some eastern Australian open forests and woodlands. The six biome structural land cover classification showed some significant deviations in class allocation compared to the SCAV particularly where grasslands are allocated to shrubland, savanna woodlands are allocated to shrubland, savanna and broadleaf forest, and open forests are allocated to savanna and broadleaf forest. The land cover and LAI products could benefit from some additional examination of Australian data addressing the structural representation of Eucalypt canopies in the “space of canopy realisation” for savanna and broadleaf forest classes.